1. Field of the Invention
The present invention relates generally to switching regulators, and more particularly to a switching regulator having a power backup unit.
2. Description of the Related Art
A prior art switching regulator having power backup unit comprises a first DC-DC converter for converting an input direct-current voltage to a desired level, and a second, power backup DC-DC converter for converting a direct-current voltage from a battery to the desired level. A first diode is provided for coupling the first output terminal of the first DC-DC converter to the first input terminal of the second converter, the second output terminal of the first converter being connected direct to the second input terminal of the second converter. The battery is connected through a second diode to the first input of the second converter. The output of the first converter is regulated at a level higher than the battery voltage so that under normal conditions no current is supplied from the battery to the second converter. If the output of the first converter reduces below the battery voltage, a current is supplied from the battery to the second converter via the second diode to produce a desired direct-current output voltage from the second converter, instead of from the first converter.
Since the efficiency of the prior art switching regulator during normal operation is represented by the multiplied efficiencies of the first and second converters, and since each of the converters comprises a transformer, the efficiency value is low and thus necessitated a design consideration that minimizes the power dissipation of individual components, while ensuring their safety margins. Additionally, because of the use of two transformers, the prior art switching regulator is costly, bulky, and adds extra weight to the regulator.